int Led=13;//define LED Interface
int buttonpin=3; // define the photo interrupter sensor interface
int val;//define numeric variables val
void setup()
{
pinMode(Led,OUTPUT);//define LED as output interface
pinMode(buttonpin,INPUT);//define the photo interrupter sensor output interface
}
void loop()
{
val=digitalRead(buttonpin);//digital interface will be assigned a value of 3 to read val
if(val==HIGH)//When the light sensor detects a signal is interrupted, LED flashes
{
digitalWrite(Led,HIGH);
}
else
{
digitalWrite(Led,LOW);
}
}

